1. Field of the Invention
The present invention relates to a display device and a method of driving the same. More particularly, the present invention relates to a display device that has a plurality of light-emission blocks constructed of a plurality of light-emission pulses within each field of a plasma display panel (PDP) and that displays an intermediate gradation based on a combination of the light-emission blocks, and further, the present invention relates to a method of driving this display device.
2. Description of the Related Art
Recently, along the increase in sizes of display devices, there has been a demand for thin display devices, and various kinds of thin display devices have been provided. For example, matrix panels for displaying images based on digital signals have been provided. Specifically, there have been provided gas discharge panels like PDPs, and matrix panels like DMDs (digital micromirror devices), EL (electro-luminescence) display devices, fluorescent display tubes, and liquid-crystal display devices. Among these thin display devices, the gas discharge panels can easily provide large screens because of a simple process. They, have good display quality based on a self-light-emission type, and have fast response speed. Therefore, the gas discharge panels are considered to be a most promising candidate as display devices for application to large-screens and direct-view type HDTVs (high-definition televisions).
A PDP has a plurality of light-emission blocks (sub-fields: SF) that are structured by a plurality of light-emission pulses within each field, and the PDP displays an intermediate gradation based on a combination of these light-emission blocks. Power consumed by the PDP for the light emission is proportional to the number of light-emission pulses (sustaining pulses) that contribute to the light emission. Therefore, it is possible to control the power consumption of the PDP by controlling the total number of light-emission pulses within each field. Particularly, there has been a demand for a display device that can control the number of light-emission pulses (power consumption) without degrading the image quality, and a method of driving this display device.
Conventionally, light-emission pulses are set as follows. First, a display load factor is calculated for each frame based on display data. Light-emission pulses are calculated based on the calculated display load factor for each frame, and the power consumption of the display device is controlled so as not to exceed a predetermined value. This technique is disclosed, for example, in Japanese Unexamined Patent Publication (Kokai) Nos. 06-332397 and 2000-098970.
Concretely, Japanese Unexamined Patent Publication (Kokai) No. 06-332397 discloses a flat panel display device comprising an integrating unit that integrates a number of pixel signals at a predetermined level that are given during a predetermined period, and a frequency altering unit that alters a panel driving frequency based on a result of integration by the integrating unit. Japanese Unexamined Patent Publication (Kokai) No. 2000-098970 discloses a plasma display device comprising an integrating unit that integrates-a number of pixel signals that are given during a predetermined period, in a bit signal unit for a gradation display, and a frequency altering unit that alters a sustaining discharge waveform frequency based on a result of integration by the integrating unit.
In the present specification, the term “field” is used by assuming a case in which an image of one frame is constructed of two fields of an odd-numbered field and an even-numbered field that are interlace displayed. When an image of one frame is progressively displayed, for example, the term “field” can be replaced with the term “frame”.
The prior art and the problems associated with the prior art will be described in detail later with reference to accompanying drawings.